Gastroenteritis
Although often called the stomach flu, gastroenteritis [2] is not real flu. It is caused by stomach viruses that induce symptoms such as nausea, vomiting, abdominal pain, and diarrhea. Other symptoms include fatigue and muscle aches.
If this is the cause of your stomach pain, the symptoms will typically disappear on their own after a few days. As watery diarrhea is often associated with this infection, you may become dehydrated. You must drink a lot of fluids to offset this. See a doctor if your symptoms last longer than a few days or you become severely dehydrated.